Pakistani Taliban chief Hakimullah Mehsud, left, is seen with Waliur Rehman during his meeting with media in Sararogha, a Pakistani tribal area of South Waziristan along the Afghanistan border, Oct. 4, 2009.

Ishtiaq Mehsud/AP Photo

An American official said the U.S. feels "very confident" Pakistani Taliban leader Hakimullah Mehsud was killed in a drone strike today. "They got Mehsud," the official told ABC News.

Mehsud, who the U.S. government considers one of its most wanted terrorists, died when a missile struck his vehicle shortly after he left a mosque, a Pakistani intelligence source said. Another Pakistani intelligence source and senior Taliban members confirmed Mehsud's death, though the Taliban has not officially acknowledged it.

White House National Security Council spokesperson Caitlin Hayden said her office was "not in a position" to confirm Mehsud's death.

Mehsud's death would represent one of the highest-level counter-terrorism victories for the U.S. since the death of al Qaeda leader Osama bin Laden. He is wanted for his alleged role in the 2009 suicide bombing of a CIA outpost in Khost, Afghanistan, which claimed the lives of seven Americans, including several CIA officers.

A former CIA operative who knew some of those killed in that attack told ABC News today that while Mehsud was likely "just another target" for America, his death was a little more personal for the CIA because of Mehsud's alleged connection to Khost.

"For most people, he is just another Taliban guy. But the Agency [CIA] tagged him a long time ago and, obviously, it meant more after Khost… Khost makes it real."

"It's a big takedown. He was a bad guy," the former operative said.

Another former CIA officer whose close colleague was killed in Khost said, "I don't revel in revenge killings, but that guy was a dirt bag."

Mehsud's group also claimed responsibility for the failed Times Square bombing in May 2010, the U.S. State Department says. The U.S. government had offered $5 million for information leading to Mehsud's arrest.

At least five others were killed in today's strike, according to local reports. Like other terrorist commanders, Mehsud has been declared dead before, only to resurface, alive and well.

Mehsud granted BBC News a rare interview last month in which he said he would be open to "serious talks" about peace with the Pakistani government. In the same interview, however, he said he would still target "America and its friends," the BBC reported.